You should have access to a computer with the Internet and room for the Scratch program. Scratch can be downloaded for either Windows (2000 or later) or Mac (OSX 10.4 or later).

Material Availability

Readily available

Cost

Very Low (under $20)

Safety

No issues

Abstract

Have you ever played a computer game in which a cartoon character, like a dog or a cat, moves or turns when you click on it? Have you ever wondered how characters know how far to move or how far to turn? In this computer science project, you will learn how with a simple (and free) program called Scratch, which will let you write your own computer program that tells a cartoon kitty how to draw shapes.

Objective

To determine how to draw different two-dimensional shapes using the computer language Scratch.

Share your story with Science Buddies!

Introduction

Note: This Science Buddies project idea was written using Scratch version 1.4. A new version, Scratch 2, is now available. You can use an online version of Scratch 2 in your web browser at
scratch.mit.edu, or you can download an offline version.

While Scratch 2 offers improvements over Scratch 1.4, the layout and some features have changed slightly. This means that the procedure below will not exactly match the new features of Scratch 2. If you need help using Scratch 2, you should go to the
official Scratch help page. If you would like to follow our directions exactly, you can still download Scratch 1.4 here.

What are your favorite things to draw? Pets? Trees? Flowers? Rainbows? One of the tricks that artists use when they plan a new drawing is to break down objects into smaller parts and shapes. So the ears on a cat break down into triangles. Or the beak on a bird breaks down into a cone. Shapes like circles, ovals, squares, triangles, hexagons, octagons, cylinders, and cones are the basic building blocks of any drawing.

Figure 1. In this drawing of a cat you can find many shapes, like the triangles in the ears, nose, and rug; the circles in the head and collar; the half-circles in the eyes; the oval in the body; and the rectangle in the rug.

If you look at the simplest two-dimensional (flat) shapes, shown below, you can see that some of them have angles. An angle is where a line makes a sharp turn. You can measure how sharp the turn is by using a tool called a protractor. A protractor has little marks on it, just like a ruler, but instead of measuring inches or centimeters, a protractor measures angles in degrees.

Figure 2. These are simple two-dimensional shapes: A circle, square, triangle, hexagon, octagon, and a line.

Figure 3. This is the math tool called a protractor that is used to measure the angles in two-dimensional shapes. The protractor in this example is measuring 35 degrees.

Pretend that you want to teach a friend how to draw a square. You decide to walk the path of a square on the floor so that you can show the friend what she has to do. You can see below that to draw a square, you would start walking at point A, travel to point B, and then turn (or rotate) 90 degrees, so that you can reach point C. Then you turn 90 degrees again to get to point D. Finally, you walk some more until you come back to point A.

Now suppose your friend tells you that she wants to learn how to draw a triangle, so you show her that path, too. To draw a triangle, you start at Point A, travel to Point B, and then have to turn very far—120 degrees—so that you can continue on the path to Point C. Then you have to turn 120 degrees again, so that you can come back to Point A.

Now suppose your friend tells you that she wants to learn how to draw a triangle, so you show her that path, too. To draw a triangle, you start at Point A, travel to Point B, and then have to turn very far—120 degrees—so that you can continue on the path to Point C. Then you have to turn 120 degrees again, so that you can come back to Point A.

In this computer science project, you are going to teach a kitty how to draw. The kitty is a cartoon character who is just a beginning artist. She doesn't even know how to draw shapes, like a triangle, yet. You'll help her by writing a simple computer program—a set of instructions for the computer. The computer program will tell her how to move so that she can draw her first shapes and get her start becoming a great artist!

Terms and Concepts

Angle

Protractor

Degree

Computer program

Questions

What does an artist do first when he or she wants to draw something?

What does a protractor help you measure?

If you wanted to draw a big shape in the sand or in the snow with your feet, how would you move your body to do it?

News Feed on This Topic

,
,

Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed

Materials and Equipment

Note: This Science Buddies project idea was written using Scratch version 1.4. A new version, Scratch 2, is now available. You can use an online version of Scratch 2 in your web browser at
scratch.mit.edu, or you can download an offline version.

While Scratch 2 offers improvements over Scratch 1.4, the layout and some features have changed slightly. This means that the procedure below will not exactly match the new features of Scratch 2. If you need help using Scratch 2, you should go to the
official Scratch help page. If you would like to follow our directions exactly, you can still download Scratch 1.4 here.

Personal computer with Internet access and the computer program Scratch installed; see the Experimental Procedure for details on installing Scratch for free.

Adult helper

Protractor

Lab notebook

Share your story with Science Buddies!

Experimental Procedure

Note: This Science Buddies project idea was written using Scratch version 1.4. A new version, Scratch 2, is now available. You can use an online version of Scratch 2 in your web browser at
scratch.mit.edu, or you can download an offline version.

While Scratch 2 offers improvements over Scratch 1.4, the layout and some features have changed slightly. This means that the procedure below will not exactly match the new features of Scratch 2. If you need help using Scratch 2, you should go to the
official Scratch help page. If you would like to follow our directions exactly, you can still download Scratch 1.4 here.

Installing and Getting Started with Scratch

To start this science fair project, you should go to the Scratch download page at scratch.mit.edu/download and have an adult help you follow the instructions there to download and install Scratch for free. If you need help installing it, read the Science Buddies Installing and Getting Started with Scratch page. This short guide will familiarize you with Scratch.

If this is your first time using Scratch or if you need a refresher, read the Science Buddies Scratch User Guide.

When you first start up Scratch, you'll see your artist cat come up on the screen. Meow! It's time to program Kitty so that she can draw shapes.

If you want to change the way Kitty looks before you start, read the Variations section, below the Experimental Procedure, to find out how.

Writing Instructions for the Kitty

The first thing Kitty needs to learn is when to start drawing. It's a little bit like when you run a race and someone says, "1, 2, 3...go!" You need to tell Kitty when to go. Find the symbol with the green flag (think of how green traffic lights mean go) under the Control category, and drag it to the center panel.

Now Kitty must erase any previous drawings so that she can start out with a fresh page. It's kind of like getting a fresh sheet of paper with no marks on it. Go to the Pen category and get the Clear element and snap it onto the flag. The Clear element clears the page.

The next thing you need to tell Kitty is where to start drawing her shapes. The center of the screen where Kitty will be drawing has the coordinates x=0 and y=0. This is a good place to start drawing, but if you want to tell her to choose a different spot, feel free to do so, using the instructions below.

To tell Kitty to go to the starting point (indicated by the green circle) and start drawing, you need to find the Go To instruction under the Motion category, which looks like this:

Drag this Go To element to the center panel and snap it onto the "Clear" element. Be sure to enter a 0 for x and a 0 for y, if those numbers are not already there and if those are the coordinates at which you want Kitty to start.

It's time to choose a color for Kitty's pen. Go to the Pen category and find the element that says "Set Pen Color to..." and is followed by a colored block (not the one followed by a white space for a number to be typed in). Drag it over to the center panel and snap it on to your "Go To x:__ y:__" element. Click on the color that you want for Kitty's pen.

Now Kitty has a pretty pen, but you have to tell her to use it! Go to the Pen category, and find the element called "Pen Down" and snap it to the bottom of your growing chain of computer language commands (called blocks). This will tell Kitty to put her pen down on the page.

Now it gets exciting. It's time for Kitty to learn how to draw her first shapes. Remember from the Introduction how you taught your friend to draw a square and a triangle using steps and angles? Go to the Motion category and take a look at the elements that begin with "Move" and "Turn."

That's exactly what you did when you walked the path of the square and the triangle—you moved and turned, moved and turned, moved and turned, over and over again until you completed the shape. So you know you're going to need those two elements in your list of instructions.

Move the "Move" and "Turn" elements to the center panel and type in some starting values, like 60 steps and 90 degrees, just to get started. You will change these values during your testing.

But how do you make Kitty do something over and over again? That's where the Control category can help you. Look at the "Repeat" element. Any instructions you put inside the repeat element will be repeated again and again!

Move the "Repeat" element to the center panel and type in a starting value of 20 (indicating to repeat 20 times). You will change this value during your testing.

Arrange the "Move," "Turn," and "Repeat" elements in a way that you think will make Kitty draw shapes. Hint: Notice the white space between the "Repeat" element's golden shape—do you think that will help you use this block? You can stuff as many blocks inside there as you want and they will all be repeated the number of times that you have set.

It's not time to test just yet. First, you need to make Kitty put the pen away and move herself out of the way after she is done drawing, so that you can see what shape she has made. Go back to the Pen category and drag over the Pen Up element, which means "Take your pen off the paper, Kitty!"

To get her to move out of the way, you want to move her to a coordinate that is away from her drawing, like the red circle shown in the graph several steps above. Use the "Go To x:__y:__" element in the Motion category again to get her to move out of the way.

Enter -150 for the x-coordinate, and 0 for the y-coordinate. Feel free to choose a different ending location.

Finally, you want Kitty to look at her masterpiece, not up in the sky or down at the ground. Choose the "Point in Direction..." element from the Motion category to get her to look right. Leave the number as is, reading 90 (which means 90 degrees).

Testing Your Computer Program

Now that your program is written, you need to test it and adjust it to get Kitty to draw certain shapes. It's time to experiment. To start running the program, just click the green flag above the white screen where you see Kitty.

What happened? Did she draw a shape? What shape is it? Experiment with the values in the "Move," "Turn," and "Repeat" elements to see what shapes you can get her to draw. Create a data table in your lab notebook, like the one below, so that you can remember what different values do in your program. If you need help with your program, read the Science Buddies Troubleshooting a Program in Scratch page.

Scratch Testing Data Table

Number of repeats

Number of steps

Turn in degrees

Shape Kitty drew

Comments on the shape, such as its size, or whether it went off the page

20

60

90

Get Kitty to draw all the basic shapes, like a line, a triangle, a square, a hexagon, an octagon, and a circle. The circle is an interesting challenge, because there are no angles, so you will have to make very small turns and get a shape that approximates a circle. Once you've completed it, would you say it's a very good approximation? Does it look like a circle to you?

Use a protractor to measure the amount of turn needed to draw each shape. For example, to draw a square, you need to turn 90 degrees. To draw a triangle, you might want to try having Kitty turn 120 degrees. These are values to test (one at a time) in your computer program. If you don't know how to use a protractor, see the link to instructions in the Bibliography.

Can you get Kitty to draw different sizes of shapes, such as a small triangle, a medium-sized triangle, and a big triangle?

Share your story with Science Buddies!

Variations

Would you like to change the way Kitty looks? Click on the Looks category for all sorts of fun things to try.

There are two elements called "Change Color Effect By…" and "Set Color Effect to…" Experiment with those to see what happens to Kitty. Can you make Kitty turn pink with one of these blocks?

Note: When you are experimenting with how something looks, it is best to add the "Clear Graphics Effects" element near the top of the chain of blocks, so that you can start with a fresh, new look each time you click on the green flag.

Once you understand what these blocks do for the word Color, click on the word "Color" in each element and you can see even more exciting things to try, like changing "Fisheye," "Whirl," "Pixelate," "Mosaic," "Brightness," and "Ghost." Experiment again to see what each of those does. Is there one you like best? Is there a block that has the power to turn one kitty into many kittens?

Another way to change Kitty's look is with the "Switch to Costume" element. You first have to go to the center panel and click on the Costume tab. Then, either draw something yourself with the tools there, or import (bring in) something that you want to change Kitty into, like a puppy or a fish from one of the folders that you see, like the Animals or Fantasy folders.

And, just for fun, you can always make Kitty say something at the end of her drawing, like "Ta Da!" or "Where did Kitty go?" (if she has changed into a different animal). The "Say" elements allow you to have Kitty say whatever you wish.

If you can teach Kitty how to draw equilateral shapes (shapes that have sides that are the same length), can you teach her how to draw shapes with sides of different lengths, like a rectangle?

When you were testing your program, did Kitty draw some unusual shapes that look like flowers? Or beautiful lace? Can you make Kitty color in the flowers by changing the pen size? Can you make Kitty draw a whole flower garden? Make sure she draws herself some catnip!

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Related Links

If you like this project, you might enjoy exploring these related careers:

Computer Programmer

Computers are essential tools in the modern world, handling everything from traffic control, car welding, movie animation, shipping, aircraft design, and social networking to book publishing, business management, music mixing, health care, agriculture, and online shopping. Computer programmers are the people who write the instructions that tell computers what to do.
Read more

Mathematician

Mathematicians are part of an ancient tradition of searching for patterns, conjecturing, and figuring out truths based on rigorous deduction. Some mathematicians focus on purely theoretical problems, with no obvious or immediate applications, except to advance our understanding of mathematics, while others focus on applied mathematics, where they try to solve problems in economics, business, science, physics, or engineering.
Read more

News Feed on This Topic

,
,

Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed

Looking for more science fun?

Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.

Can you suggest any improvements or ideas?(Enter "no" if you have none.)

characters left

Overall, how would you rate the quality of this project?

Excellent
Very good
Good
OK
Poor

What is your enthusiasm for science after doing your project?

Very high
High
Moderate
Low
Very low

Compared to a typical science class, please tell us how much you learned doing this project.

Much more
More
About the same
Less
Much less

Optional:Attach a picture of your project (JPG, JPEG, GIF, PNG only)

Optional:Caption for picture

characters left

You can find this page online at: http://www.sciencebuddies.org/science-fair-projects/project_ideas/CompSci_p035.shtml

You may print and distribute up to 200 copies of this document annually, at no charge, for personal and classroom educational use. When printing this document, you may NOT modify it in any way. For any other use, please contact Science Buddies.